The present invention relates generally to fluid cylinders and more specifically to an improved non-pressure head of a brake cylinder.
Two presently used brake cylinders used in freight trains are illustrated in FIGS. 1-3. A cylinder portion 12 being a non-pressure side is connected to a non-pressure head portion 30. A piston 24 and piston rod 26 ride within the cylinder portion 12.
When the non-pressure head 30 was designed, the piston stop 36, shown in FIG. 1 and known as the chimney, was welded into the center of the non-pressure head 30. The piston stop 36 functions also as a spring guide, keeping the spring 46 axially aligned with the piston rod 26. In 1995, as markets became more competitive, the non-pressure head 30 was targeted for cost reduction. Since the chimney 36 was manually welded onto the non-pressure head 30 (a labor intense process), it was targeted for redesign.
Eliminating the chimney presented two problems. One problem was that the piston retaining or stop feature needed to be replaced. The other problem was that the spring needed to be guided in a different manner.
The piston stop function was accomplished by forming two flange extensions 37 in the flange area 32 of the non-pressure head 30′, as shown in FIG. 2. The flange extensions 37 are approximately 7 13/16″ apart, which is less that the OD of the piston 24. When the piston 24 contacted these flat features 37, the piston 24 stopped traveling, thus retaining the piston in the cylinder bore. A piece of plastic 48 was designed in a helical shape at the same pitch as the return spring 46 in its free state. It is thick enough to evenly fill the gap between the piston rod 26 and the return spring 46 and act as a guide.
The interface of the non-pressure head 30, 30′ with the brake cylinder 12 is sealed by a gasket 50. The gasket 50, in conjunction with the piston rod gasket, seals the non-pressure cavity from the atmosphere, keeping contaminants out. The non-pressure cavity volume changes as the piston 24 strokes to and fro with brake cylinder signal. A vent is required to allow the non-pressure cavity volume to react to the change in volume. The vent 60 (shown in FIGS. 2 and 3) is built into the head portion 34. The vent cavity 60 is attached to the side of the head portion 34. To keep debris out of the non-pressure cavity, the vent opening is filtered with a piece of open celled foam 62 held by clasp 64.
The location of the vent 60 is not at the lowest point of the non-pressure head's cavity. As a result, in the event of water intrusion, possibly through condensation or gasket failure, the water cannot escape and corrosion results. Because the vent housing 60, known as the strainer case, is welded to the side of the non-pressure head, it impedes stacking one non-pressure head on top of another. This stackability is desirable because it facilitates efficient shipping and stocking. The labor intense welding process involved to secure the strainer case results in high product costs. Also, the two-sided piston stop 37 may not support the piston symmetrically causing uneven loading of the piston.
The presently disclosed non-pressure head for a fluid cylinder addresses these issues and includes a drain channel formed in the flange by a raised portion of the flange extending from a plane of the flange in the same direction as the head portion. The channel is cold formed in the flange. For the piston stop, the flange has an opening of a diameter smaller than a diameter of a piston on the piston rod to form a stop for the piston portion. A plurality of spaced ribs are provided between the flange and the head. The ribs are raised portions of the flange and the head and are cold formed in the flange and the head.
The disclosed non-pressure head may be part of a kit for a fluid cylinder, which further includes a compressible, porous material to be positioned between a pressure head and the flange and having a thickness at least as large as the depth of the channel. An annular gasket may also be in the kit, and the porous material is joined to the gasket.
Also disclosed is a fluid cylinder having a pressure head and a non-pressure head joined at respective annular flanges and an annular gasket between the flanges. A piston moves in the pressure head and is mounted to a piston rod extending through and exiting the non-pressure head at an opening. A drain channel is provided in the flange of the non-pressure head facing the channel. The drain channel is a raised portion of the flange extending from a plane of the flange. The channel is cold formed in the flange. A compressible, porous material is between the gasket and the flange of the non-pressure head and has a thickness at least as large as the depth of the channel. The porous material is joined to the gasket as a unit.
These and other aspects of the present disclosure will become apparent from the following detailed description of the disclosure, when considered in conjunction with accompanying drawings.